Your comparison--- with some valid points in description, is largely at fault.
Comparing Sq. rumba , Bolero and or Intern.. style , is an Apples and Oranges situation.
Yes, they are linked musically, but they depart in different directions, due to musical and figurative construction, as we well know .

The stressing of close foot contact with the floor in the Intern. style, is quite frequently ignored in the American style ( and I should say , truer ) versions .

The commencement of each, is also completely different, thus placing a totally different accent, on the musical interpretation.

By changing this, it requires different techniques, to attain the desired result for the " standard ".

If one goes back to origins ( Danzon to Systemo Cubano ) it becomes abundantly clear, where the intended " direction" of the dance was meant to be.

As in most cases, where social application is applied, changes are frequently made, to adapt to a ballroom
concept, thus eroding its core value to some degree .